This domain is found in the yeast cell wall assembly regulator SMI1 and the cell proliferation protein KNR4 [(PUBMED:7937796), (PUBMED:8289782)].

Saccharomyces cerevisiae protein Smi1 has a regulatory role in chitin deposition and in cell wall assembly [(PUBMED:10206705)].

KNR4 is believed to connect the PKC1-SLT2 MAPK pathway with cell proliferation. It has been shown to interact with BCK2, a gene involved in cell cycle progression in S. cerevisiae (forming a complex) to allow PKC1 to coordinate the cell cycle (cell proliferation) with cell wall integrity [(PUBMED:12185498), (PUBMED:12823808)]. KNR4 also interacts with the tyrosine-tRNA synthetase protein encoded by TYS1 and is involved in sporulation process [(PUBMED:11410349)].

Proteins containing this domain also include the animal F-box only protein 3 (FBXO3). In humans, FBXO3 is a substrate recognition component of the SCF (SKP1-CUL1-F-box protein)-type E3 ubiquitin ligase complex [(PUBMED:18809579)].

Note: previously reported evidence that KNR4 may interact with nuclear matrix-association region [(PUBMED:8516310)] may be due to an artefact [(PUBMED:10206705)].

k9 killer toxin from Hansenula mrakii was used to select a number ofresistant mutants from Saccharomyces cerevisiae. Preliminary biochemicaland genetic studies showed that some of them acquired structural defectsin the cell wall. One of these mutants, the knr4-1 mutant, displays anumber of cell wall defects, including osmotic sensitivity; sensitivity tocercosporamide, a known antifungal agent; and resistance to Zymolyase, a(1,3)-beta-glucanase. We report here the isolation and analysis of theKNR4 gene. DNA sequence analysis revealed an uninterrupted open readingframe which contains five potential start codons. The longest codingtemplate encodes a protein of 505 amino acids with a calculated molecularmass of 57,044 Da. A data base search revealed 100% identity with anuclear protein, SMI1p. Disruption of the KNR4 locus does not result incell death; however, it leads to reduced levels of both (1,3)-beta-glucansynthase activity and (1,3)-beta-glucan content in the cell wall. The genewas mapped to the right arm of chromosome VII.